Spice tests update.

Part of Spice work we've been working on for last 4 months. Single patches contain changes related to multiple tests.
Brief description of changes (more in commit messages):
- Added smartcard tests (smart_setup.py and rv_smartcard) with needed changes in qemu_vm.py
- Added rv_clearx which restarts only X which is good enough for VM to be used for next tests.
- Added simple tests of start/restart/stop of spice vdagent deamon (rv_vdagent.py).
- Added possibility for spice server to listen on pseudo IPV6 and spice client to connect to such qemu instance (qemu_vm.py, rv_connect.py).
- Added rv_audio test which plays sound on guest and records on client machine, allows only small hiccups. Variants of migration during playback (rv_audio.py) and Disabling audio with remote-viewer command line option (rv_connect.py)
- Added support for various using SSL subject of the host cert when connecting over SSL (rv_connect.py).
- Added rv_video test which plays video file on the guest.
- Support for connecting with using remote-viewer to a guest through Menu of remote-viewer, instead of using full command line.
- Replaced rv_disconnect with generic kill-app.
- Related updates in spice.cfg and tests-spice.cfg files.